By Deba Hafizi
The latest potential safeguard to prevent the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, can be found in almost every kitchen pantry — salt! Canadian and international researchers are examining whether coating masks, air filters, and high-touch surfaces with sodium chloride (salt) might help prevent the spread of SARS-CoV-2 and other viruses and bacteria.
In a recent issue of Health Technology Update, CADTH looked at the latest research on compressed salt surfaces for reducing the transmission of viruses and bacteria. CADTH is an independent agency that finds, assesses, and summarizes the research on drugs, medical devices, tests, and procedures. The CADTH Health Technology Update newsletter describes new and emerging health technologies that are likely to have a significant impact on health care in Canada.
Salt is a natural substance that inhibits the growth of bacteria and has long been used in food preservation, flavouring, pharmaceuticals, agriculture, and at-home remedies. The theory behind salt’s potential ability to inhibit SARS-CoV-2 is that when droplets containing virus particles encounter a salt-coated surface, the water in the droplets dissolves some of the salt. When the water evaporates, the salt recrystallizes and the jagged salt crystals pierce the virus membrane, ultimately killing it. This method has been tested against influenza viruses and bacteria and has been proven to be effective. Compressed salt is therefore being investigated as an antimicrobial for use on high-touch surfaces — such as door push plates, bed rails, and taps — by an Alberta company, Outbreaker Solutions Technologies. Pilot evaluations of Outbreaker products (compressed salt-coated surfaces) have been carried out at several Alberta facilities. A 2016 pilot study found that a compressed sodium chloride surface reduced contamination with the methicillin-resistant Staphylococcus aureus (MRSA) bacteria by 94 per cent within the first 60 seconds compared with 71 to 73 per cent for copper surfaces. Outbreaker is currently investigating whether these salt-coated surfaces will have a similar impact against SARS-CoV-2.
Other salt-related developments are also underway, including salt-coated facial masks and air filter materials, as well as a saltwater soaking solution for household materials and cloth masks. A team from the University of Alberta found that salt-coated facial masks effectively deactivated influenza virus aerosols and bacteria bio-aerosols and is currently investigating whether it will also protect against SARS-CoV-2, which has a similar morphology to other tested viruses. Elsewhere, a research team in Boston investigated whether saltwater-soaked materials — such as paper towels and surgical masks — were able to filter out particles the size of viruses in droplet testing. The investigators found that there was a decrease in bacterial growth on masks they had contaminated with E. coli, especially in portions with higher salt saturation. These findings suggest that salt-water treated kitchen paper towels could be an inexpensive and accessible way to add additional layer of protection for people wearing homemade cloth masks or for health care workers who need to extend the life of their personal protective equipment, or PPE.
While these technologies show promise, they have not been tested against SARS-CoV-2 nor have they been vetted or recommended by any federal or public health authorities for use on surfaces or facial masks.
While salt may have antimicrobial properties when applied to surfaces and materials, this doesn’t mean that injecting it or spraying it up the nose can prevent or cure COVID-19. Much like bleach, which has antimicrobial properties and is used on everyday surfaces in your home, it does not mean it will have the same effect in the body; in fact, ingesting bleach can be harmful! Salt, on the other hand, is generally safe for consumption and is often found in your favourite dishes, however, at high temperatures it can produce a vapor that is an eye irritant, and ingesting high doses can be toxic to humans and animals.
While there is currently no evidence that certain surfaces or surface coatings can halt or inhibit the growth of SARS-CoV-2, Health Canada has compiled a list of hard-surface disinfectants with evidence against the virus. Investigation of new technologies continues as we learn more about the virus. As schools and public spaces re-open, increasing the effectiveness of masks and antimicrobial surfaces could be a positive preventive public health intervention.
For more information, read the Health Technology Update newsletter at cadth.ca/health-technology-update-issue-27-0. If you’d like to learn more about CADTH, visit cadth.ca, follow us on Twitter @CADTH_ACMTS, or speak to a Liaison Officer in your region: cadth.ca/Liaison-Officers. To suggest a new or emerging health technology for CADTH to review, email us at HorizonScanning@cadth.ca.
Deba Hafizi is a knowledge mobilization officer at CADTH.